DETECTION OF VIRUSES BY NANOWIRES
Nanowires are what their name suggests. They have nanoscale diameters but may be several microns long. They may be metallic and act as electrical conductors or they may be made from semiconductor materials.
Biosensors can be made using silicon semiconductor nanowires. These may be coated with antibodies that bind to a specific virus. Binding of the virus to the antibody triggers a change in conductance of the nanowire. For a p-type silicon nanowire, the conductance decreases when the surface charge on the virus particle is positive and, conversely, increases if the virus surface is negative. Single viruses may be detected by this approach (Fig. 7.14). It is also possible to attach single-stranded DNA to the nanowire. In this case, conductance changes are triggered by binding of the complementary single strand. Possible future applications include both clinical testing and sensors for monitoring food, water, and air for public health and/or biodefense.
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